Flashcards in Preterm labour Deck (49)
What is term?
Period between 37-42 completed weeks of gestation
What is post term?
Strictly period after 42 weeks gestation
Period between 23-36 completed weeks of gestation
What is human preterm labour generally defined as?
Presence of uterine contractions and progressive cervical effacement and dilation occurring between 23-36 completed weeks of gestation
What is important to consider as well as gestation length in preterm labour?
Birthweight; often increases parallel with gestation length but pathological situations may change relationship.
What is the normal birthweight for a term infant?
2500 - 4000g; mean 3250g
Why is estimated date of confinement essential?
To allow reliable subsequent determination of normality of gestation length and birthweight
What are the conditions which may contribute to preterm labour? (have etiological association)
-Previous preterm birth
-APH (esp abruption)
- cervical insufficiency
-Infection: genital tract or abdominopelvic structures; systemic (flu)
-Uterine abnormality: congenital, fibroids
-Placental insufficiency: PET, maternal disease (renal, autoimmune, thombophilia)
When does uterine over distension occur?
Polyhydramnios and multiple gestations
What are the pathogens which commonly infect the genital tract and trigger preterm labour?
What uterine abnormalities may precipitate pre term labour?
-incomplete Mullerian duplications (e.g. subseptate uterus)
What are the environmental / social causes of pre term labour?
-Tobacco / smoking
-Illicit drugs (coke, crack)
-Sexual activity (weak)
-Exercise (weak if reasonable exercise)
Presentation preterm labour?
-Increase in uterine contractions
-Sudden loss of clear fluid (i.e. membrane rupture)
-Sudden increase in vaginal discharge
How is preterm labour diagnosed?
-Hx: contraction details, EDD
-PEx: sterile spec, exclude ROM, progressive cervical effacement and dilation
-Ix: foetal fibronectin, amnisure
Why is a sterile speculum exam conducted in suspected preterm labour?
-Check for cervical changes
-Check for ruptured membranes
-Exclude cord prolapse
-allow micro swab of cervix, amnisure if required
-abdo palpation of uterus for contractions
Initial management of preterm labour?
-Aetiology and Rx if appropriate
-Admit to perinatal centre with appropriate facilities; neonatal team aware
-Observe (hours) and assess for cervical change
-Foetal fibronectin swab
-Consider: CST and MgSO4, GBS prophylaxis
What is foetal fibronectin?
Choriodecidual glycoprotein released into the vagina at a preclinical stage of preterm labour
What must be decided once preterm labour diagnosed?
Advisability of tocolytic therapy
Contraindications to IV salbutamol in preterm labour tocolysis?
-Diabetes (causes hyperglycemia)
-maternal cardiac disease (tacky)
-APH (subverts normal CV homestatic mechanisms)
-ROM (age dependent; risk of chorioamnionitis outweigh benefit)
-Cervical dilation >4cm
-Genital tract infection
-FDIU or abnormality incompatible with life
Why is tocolysis contraindicated with cervical dilation >4cm?
Tocolysis ineffective by that stage
What is the current drug of choice as a tocolytic?
Why can't IV salbutamol and PO nifedipine be given together?
CV side effects: hypotension, tachycardia, palpitations
What are the options for tocolysis?
-Indomethacin (PG synthesis inhibitor)
-Atosiban (oxytocin receptor antagonist)
What is the main utility of tocolysis given their disappointing effect on perinatal outcomes?
-1) Maintaining uterine quiescence during transfer of a patient in preterm labour
-2) Maintaining foetus in utero for 24-48h to allow medications for foetal lung development
How may the incidence of neonatal respiratory distress be dramatically reduced?
Corticosteroids given maternally 24-48h prior to delivery between 26-32 weeks gestation
Why are corticosteroids effective in reducing neonatal respiratory distress?
Cross placenta and trigger production of lung surfactant in the foetus
What other conditions are improved by the maternal administration of corticosteroids?
How is incidence of CP reduced?
Magnesium sulphate administered IV to mother at risk of early preterm
Foetal factors to consider in mode of delivery in preterm labour?